How to put a scrollbar in my tumblelog?

I want there to be a scrollbar over in the section where it shows who I’m following.
(troubleinharlem.tumblr.com)

Okay, right now the CSS looks like this :
{block:ifshowpeopleifollow}
<p>{text:name of tumbleroll}</p>
{block:Following}
<div class=“follow” style=“overflow: auto; height: 210px; width: 240px;”>
{block:Followed}
<a href=”{FollowedURL}”><img src=”{FollowedPortraitURL-24}” border=“1”></a>
{/block:Followed}
{/block:Following}
</div>
{/block:ifshowpeopleifollow}

I used the advice from @johnpowell (the part that says div class=“follow”) but it isn’t working.

What did I do wrong and how can I fix it?